Abstract
Purpose: :
To describe the detailed localization of two oxygen–binding proteins neuroglobin (Ngb) and cytoglobin (Cygb), in the anterior segment of the healthy human and dog eyes and determine whether these proteins co–localize within the same cell types.
Methods: :
Polyclonal anti–Ngb and anti–Cygb antibodies and a monoclonal anti–Ngb antibody were used to examine the distribution pattern of Ngb and Cygb in sections of human and dog anterior eye segments. The anterior segment structures examined included ciliary body, iris, trabecular meshwork and canal of Schlemm in the iridocorneal angle, lens, and cornea. Tissue sections were visualized and images captured with a confocal scanning laser microscope and conventional upright microscope.
Results: :
Immunohistochemical analysis of healthy human and dog eye sections showed strong Ngb and Cygb immunoreactivity (IR) in the non–pigmented ciliary epithelium of the pars plana and pars plicata of the ciliary body, as well as in ciliary body musculature. In the iris, Ngb and Cygb–IR was localized to the fibroblasts in the anterior border and the stroma, iridal sphincter and dilator muscle. Furthermore, in the iridocorneal angle, both Ngb and Cygb were detected in endothelial cells of the human and dog trabecular meshwork and canal of Schlemm in human tissue sections. Weak Ngb and Cygb–IR was detected in the lens epithelium. In the cornea, Ngb– and Cygb–IR was localized to the corneal epithelium and endothelium. Ngb and Cygb distribution was consistent between human and dog anterior segments. Furthermore, Ngb and Cygb were co–localized within the same cells in all structures examined.
Conclusions: :
Ngb and Cygb, two recent additions to the globin family, are co–localized within the same structures of the healthy human and dog anterior eye segment. Based on Ngb and Cygb localization and their previously reported biochemical features, we hypothesize that Ngb and Cygb may function as scavengers of reactive oxygen species and/or facilitators of oxygen diffusion, and thus may mediate oxygenation of the avascular ocular structures – the cornea and lens.
Keywords: microscopy: light/fluorescence/immunohistochemistry • oxidation/oxidative or free radical damage